Why are the transitions in a Caesium atom called D1 and D2?

[TheDestroyer]

Hello people,

I was just wondering about the names of the transitions in a Caesium atom. Why are the transitions from 6P(1/2) to 6S(1/2) and from 6P(3/2) to 6S(1/2) called D1 and D2 respectively? is it just a conventional "name"?

Thank you for any efforts.

 

[TheDestroyer]

OMG... is the question that difficult? come on guys!

Probably this explains why google doesn't have a single answer :(

 

[tiny-tim]

Hello TheDestroyer!

The names come from spectroscopy.

See http://en.wikipedia.org/wiki/Fraunhofer_lines" …

The D₁ and D₂ lines form the well-known "sodium doublet", the centre wavelength of which (589.29 nm) is given the designation letter "D".

This historical designation for this line has stuck and is given to the all the transitions between the ground state and the first excited state of the other alkali atoms as well.

The D₁ and D₂ lines correspond to the fine splitting of the excited states. This may be confusing because the excited state for this transition is the P-state of the alkali and should not be confused with the higher D-states​

 

[TheDestroyer]

Thank you so much pal :). I got it!